1. Field of the Invention
The present invention relates to a method and an apparatus for visual inspection of a bump array formed on a base material such as a flip chip.
2. Description of the Related Art
Regarding a flip chip on which a bump array is formed, a high-density mounting is enabled by bonding the tops of the bumps onto a substrate. If there exists differences in the height of the bumps, insufficient connection and/or non-connection may occur after the bumps are bonded to a substrate, and if the diameter of a bump is excessively large, a short-circuiting with an adjacent bump may occur. Although these defectiveness can be detected by an electric test after mounting the flip chip onto a substrate, it is preferable that they are detected by a visual inspection before mounting a flip chip.
Therefore, a visual inspection apparatus is used in order to judge the quality of bumps by measuring one or more of the height, diameter or volume of bumps on the basis of triangulation, etc., with irradiating a laser beam to an object to be inspected and receiving the reflected light with a sensor.
However, since thousands of bumps are arranged on a chip, the time for a visual inspection of bumps is relatively longer. In particular, as shown in FIGS. 37(A) and 37(B), in a case where a visual inspection is carried out with respect to bumps 12 which are arrayed and bonded onto the respective chip areas 11 before dividing the wafer into chips with a number of chip areas 11 formed on a wafer 10, a higher speed inspection is required.
Further, although the array figure of bumps differs according to the kinds of chips, in the prior art, an object to be inspected is fed in zigzag regardless of the bump array figure. This results in a longer feed time.